This study aims to use manganese-enhanced MRI (MEMRI) to investigate the progression and permanence of the gray matter injuries in a neonatal rat model by mild hypoxic-ischemia (H-I) insult. Histological analyses were performed using staining for Mn superoxide dismutase (Mn-SOD) and glutamine synthetase (GS), which are Mn-binding enzymes against oxidative stress and glutamate excitotoxicity in neurodegeneration, and the standard hematoxylin and eosin (H&E). The transient changes associated with gray matter injuries in T(2)-weighted image (T2WI) and diffusion weighted image (DWI) in acute phase were shown to be detectable using MEMRI in late phase by systemic Mn(2+) administration, correlating with the local cell death, GS and Mn-SOD increase. Therefore, MEMRI may be a potentially useful diagnostic paradigm for detecting the gray matter injuries that are otherwise undetectable using the current MRI techniques in late phase of mild H-I injury.